This invention relates to a fertilizer solution comprising zinc nitrate, ammonium nitrate and urea in aqueous solution; in particular, it relates to the inhibition of the corrosive action thereof on carbon steel.
The use of micronutrients as fertilizers is experiencing increased use. The elements such as zinc, manganese, boron, copper, molybdenum and iron are fully as important as the primary nutrients, nitrogen, phosphorus, and potassium, although the former are used in much smaller quantities. Agronomic tests in a large number of states have been concerned with establishing where the need for micronutrients exists, comparing sources and carriers and indicating amounts that may be needed.
It is now known that plants growing on soils having pH values over 7.0 usually suffer from lack of zinc availability in the soil due to the presence of various calcium compounds. Therefore, zinc is usually supplied to the plants by foliar means. However, foliar application of zinc compositions has been the subject of considerable research in recent years because of relatively low absorption of the micronutrient by the leaves of the plant. The most effective zinc composition discovered to date is described in U.S. application Ser. No. 553,953, filed Feb. 28, 1975, by Dr. James Benton Storey.
Said Storey application discloses that an aqueous solution containing a specified mixture of zinc nitrate, ammonium nitrate, and urea is surprisingly effective in correcting zinc deficiencies in pecan and other plants when applied as a foliar treatment. Unfortunately, these mixtures are extremely corrosive to the common steel equipment generally used in transporting and applying foliar spray solutions. Moreover, none of the common materials used to inhibit corrosion by fertilizer solutions such as phosphates, chromates, and borates, are satisfactory for use with these mixtures. Accordingly, an effective corrosion inhibitor is urgently needed. Desirably, the corrosion inhibitor should reduce corrosion to 1 to 10 mils per year or less; it should be in water-soluble form for easy mixing with the aqueous zinc-containing foliar spray solution; and it should not cause environmental problems upon use.